Dimmable LED-based MR16 lighting apparatus methods

ABSTRACT

Methods and apparatus for providing controllable power via an A.C. power source to LED-based lighting devices having an MR16 configuration. In one example, LED-based MR16 lighting devices may be coupled to A.C. power circuits that are controlled by conventional dimmers (i.e, “A.C. dimmer circuits”). In yet other aspects, one or more parameters relating to the light generated by LED-based light sources (e.g., intensity, color, color temperature, temporal characteristics, etc.) may be conveniently controlled via operation of a conventional A.C. dimmer and/or other signals present on the A.C. power circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit, under 35 U.S.C. §119(e), ofU.S. Provisional Application Ser. No. 60/558,235, filed Mar. 31, 2004,entitled “Methods and Apparatus for Providing Power to LightingDevices.”

This application also claims the benefit, under 35 U.S.C. §120, as acontinuation-in-part (CIP) of U.S. Non-provisional application Ser. No.10/435,687, filed May 9, 2003, entitled “Method and Apparatus forProviding Power to Lighting Devices,” which in turn claims priority toU.S. Provisional Application Ser. No. 60/379,079, filed May 9, 2002,entitled “Systems and Methods for Controlling LED Based Lighting,” andU.S. Provisional Application Ser. No. 60/391,627, filed June 26, 2002,entitled “Switched Current Sink.”

Each of the foregoing applications is hereby incorporated herein byreference.

FIELD OF THE INVENTION

The present invention is directed generally to methods and apparatus forproviding power to devices on A.C. power circuits. More particularly,the invention relates to methods and apparatus for providing power tolight emitting diode (LED) based devices, primarily for illuminationpurposes.

BACKGROUND

In various lighting applications (e.g., home, commercial, industrial,etc.), there are instances in which it is desirable to adjust the amountof light generated by one or more conventional light sources (e.g.,incandescent light bulbs, fluorescent light fixtures, etc.). In manycases, this is accomplished via a user-operated device, commonlyreferred to as a “dimmer,” that adjusts the power delivered to the lightsource(s). Many types of conventional dimmers are known that allow auser to adjust the light output of one or more light sources via sometype of user interface (e.g., by turning a knob, moving a slider, etc.,often mounted on a wall in proximity to an area in which it is desirableto adjust the light level). The user interface of some dimmers also maybe equipped with a switching/adjustment mechanism that allows one ormore light sources to be switched off and on instantaneously, and alsohave their light output gradually varied when switched on.

Many lighting systems for general interior or exterior illuminationoften are powered by an A.C. source, commonly referred to as a “linevoltage” (e.g., 120 Volts RMS at 60 Hz, 220 Volts RMS at 50 Hz). Aconventional A.C. dimmer typically receives the A.C. line voltage as aninput, and provides an A.C. signal output having one or more variableparameters that have the effect of adjusting the average voltage of theoutput signal (and hence the capability of the A.C. output signal todeliver power) in response to user operation of the dimmer. This dimmeroutput signal generally is applied, for example, to one or more lightsources that are mounted in conventional sockets or fixtures coupled tothe dimmer output (such sockets or fixtures sometimes are referred to asbeing on a “dimmer circuit”).

Conventional A.C. dimmers may be configured to control power deliveredto one Is or more light sources in one of a few different ways. Forexample, in one implementation, the adjustment of the user interfacecauses the dimmer to increase or decrease a voltage amplitude of theA.C. dimmer output signal. More commonly, however, in otherimplementations, the adjustment of the user interface causes the dimmerto adjust the duty cycle of the A.C. dimmer output signal (e.g., by“chopping- out” portions of A.C. voltage cycles). This techniquesometimes is referred to as “angle modulation” (based on the adjustablephase angle of the output signal). Perhaps the most commonly useddimmers of this type employ a triac that is selectively operated toadjust the duty cycle (i.e., modulate the phase angle) of the dimmeroutput signal by chopping- off rising portions of A.C. voltagehalf-cycles (i.e., after zero-crossings and before peaks). Other typesof dimmers that adjust duty cycles may employ gate turn-off (GTO)thyristors that are selectively operated to chop-off falling portions ofA.C. voltage half- cycles (i.e., after peaks and before zero-crossings).

FIG. 1 generally illustrates some conventional A.C. dimmerimplementations. In particular, FIG. 1 shows an example of an A.C.voltage waveform 302 (e.g., representing a standard line voltage) thatmay provide power to one or more conventional light sources. FIG. 1 alsoshows a generalized A.C. dimmer 304 responsive to a user interface 305.In the first implementation discussed above, the dimmer 304 isconfigured to output the waveform 308, in which the amplitude 307 of thedimmer output signal may be adjusted via the user interface 305. In thesecond implementation discussed above, the dimmer 304 is configured tooutput the waveform 309, in which the duty cycle 306 of the waveform 309may be adjusted via the user interface 305.

As discussed above, both of the foregoing techniques have the effect ofadjusting the average voltage applied to the light source(s), which inturn adjusts the intensity of light generated by the source(s).Incandescent sources are particularly well-suited for this type ofoperation, as they produce light when there is current flowing through afilament in either direction; as the average voltage of an A.C. signalapplied to the source(s) is adjusted (e.g., either by an adjustment ofvoltage amplitude or duty cycle), the current (and hence the power)delivered to the light source also is changed and the correspondinglight output changes. With respect to the duty cycle technique, thefilament of an incandescent source has thermal inertia and does not stopemitting light completely during short periods of voltage interruption.Accordingly, the generated light as perceived by the human eye does notappear to flicker when the voltage is “chopped,” but rather appears togradually change.

SUMMARY

The present invention is directed generally to methods and apparatus forproviding power to devices on A.C. power circuits. More particularly,methods and apparatus according to various embodiments of the presentinvention facilitate the use of LED-based light sources on A.C. powercircuits that provide either a standard line voltage or signals otherthan standard line voltages.

In one embodiment, methods and apparatus of the invention particularlyfacilitate the use of LED-based light sources on A.C. power circuitsthat are controlled by conventional dimmers (i.e, “A.C. dimmercircuits”). In one aspect, methods and apparatus of the presentinvention facilitate convenient substitution of LED-based light sourcesin lighting environments employing A.C. dimming devices and conventionallight sources. In yet other aspects, methods and apparatus according tothe present invention facilitate the control of one or more parametersrelating to the light generated by LED-based light sources (e.g.,intensity, color, color temperature, temporal characteristics, etc.) viaoperation of a conventional A.C. dimmer and/or other signals present onthe A.C. power circuit.

More generally, one embodiment of the invention is directed to anillumination apparatus, comprising at least one LED and at least onecontroller coupled to the at least one LED. The controller is configuredto receive a power-related signal from an A.C. power source thatprovides signals other than a standard A.C. line voltage. The controllerfurther is configured to provide power to the at least one LED based onthe power-related signal.

Another embodiment of the invention is directed to an illuminationmethod, comprising an act of providing power to at least one LED basedon a power-related signal from an A.C. power source that providessignals other than a standard A.C. line voltage.

Another embodiment of the invention is directed to an illuminationapparatus, comprising at least one LED, and at least one controllercoupled to the at least one LED and configured to receive apower-related signal from an alternating current (A.C.) dimmer circuitand provide power to the at least one LED based on the power-relatedsignal.

Another embodiment of the invention is directed to an illuminationmethod, comprising an act of providing power to at least one LED basedon a power-related signal from an alternating current (A.C.) dimmercircuit.

Another embodiment of the invention is directed to an illuminationapparatus, comprising at least one LED adapted to generate anessentially white light, and at least one controller coupled to the atleast one LED and configured to receive a power-related signal from analternating current (A.C.) dimmer circuit and provide power to the atleast one LED based on the power-related signal. The A.C. dimmer circuitis controller by a user interface to vary the power-related signal. Thecontroller is configured to variably control at least one parameter ofthe essentially white light in response to operation of the userinterface so as to approximate light generation characteristics of anincandescent light source.

Another embodiment of the invention is directed to a lighting system,comprising at least one LED, a power connector, and a power converterassociated with the power connector and adapted to convert A.C. dimmercircuit power received by the power connector to form a converted power.The system also includes an adjustment circuit associated with the powerconverter adapted to adjust power delivered to the at least one LED.

Another embodiment of the invention is directed to a method of providingillumination, comprising the steps of providing an AC dimmer circuit,connecting an LED lighting system to the AC dimmer circuit, generatinglight from the LED lighting system by energizing the AC dimmer circuit,and adjusting the light generated by the LED lighting system byadjusting the AC dimmer circuit.

Another embodiment of the invention is directed to method forcontrolling at least one device powered via an A.C. line voltage. Themethod comprises an act of generating a power signal based on the A.C.line voltage, wherein the power signal provides an essentially constantpower to the at least one device and includes at least one communicationchannel carrying control information for the at least one device, the atleast one communication channel occupying a portion of a duty cycle overa period of cycles of the A.C. line voltage.

Another embodiment of the invention is directed to an apparatus forcontrolling at least one device powered via an A.C. line voltage. Theapparatus comprises a supply voltage controller configured to generate apower signal based on the A.C. line voltage, wherein the power signalprovides an essentially constant power to the at least one device andincludes at least one communication channel carrying control informationfor the at least one device, the at least one communication channeloccupying a portion of a duty cycle over a period of cycles of the A.C.line voltage. In one aspect of this embodiment, the supply voltagecontroller includes at least one user interface to provide variablecontrol information in the at least one communication channel.

Another embodiment is directed to an apparatus, comprising at least oneLED and a housing in which the at least one LED is disposed, the housingincluding at least one connection to engage mechanically andelectrically with a conventional MR16 socket. The apparatus furthercomprises at least one controller coupled to the housing and the atleast one LED and configured to receive first power from an alternatingcurrent (A.C.) dimmer circuit. The A.C. dimmer circuit is controlled bya user interface to vary the first power, and the at least onecontroller is further configured to provide second power to the at leastone LED based on the first power.

Another embodiment is directed to an apparatus, comprising at least oneLED and a housing in which the at least one LED is disposed, the housingincluding at least one connection to engage mechanically andelectrically with a conventional MR16 socket. The apparatus furthercomprises at least one controller coupled to the housing and the atleast one LED and configured to receive a power-related signal from analternating current (A.C.) power source that provides signals other thana standard A.C. line voltage. The at least one controller further isconfigured to provide power to the at least one LED based on thepower-related signal.

Another embodiment is directed to a method, comprising an act ofproviding power via a conventional MR16 socket to at least one LED,based on a power-related Is signal from an alternating current (A.C.)power source that provides signals other than a standard A.C. linevoltage.

Another embodiment is directed to an apparatus, comprising at least oneLED adapted to generate an essentially white light and a housing inwhich the at least one LED is disposed, the housing including at leastone connection to engage mechanically and electrically with aconventional MR16 socket. The apparatus further comprises at least onecontroller coupled to the at least one LED and configured to receive apower- related signal from an alternating current (A.C.) dimmer circuitand provide power to the at least one LED based on the power-relatedsignal. The A.C. dimmer circuit is controlled by a user interface tovary the power-related signal, and the at least one controller isconfigured to variably control at least one parameter of the essentiallywhite light in response to operation of the user interface so as toapproximate light generation characteristics of an incandescent lightsource.

As used herein for purposes of the present disclosure, the term “LED”should be understood to include any electroluminescent diode or othertype of carrier injection / junction-based system that is capable ofgenerating radiation in response to an electric signal. Thus, the termLED includes,. but is not limited to, various semiconductor-basedstructures that emit light in response to current, light emittingpolymers, electroluminescent strips, and the like.

In particular, the term LED refers to light emitting diodes of all types(including semi-conductor and organic light emitting diodes) that may beconfigured to generate radiation in one or more of the infraredspectrum, ultraviolet spectrum, and various portions of the visiblespectrum (generally including radiation wavelengths from approximately400 nanometers to approximately 700 nanometers). Some examples of LEDsinclude, but are not limited to, various types of infrared LEDs,ultraviolet LEDs, red LEDs, blue LEDs, green LEDs, yellow LEDs, amberLEDs, orange LEDs, and white LEDs (discussed further below). It alsoshould be appreciated that LEDs may be configured to generate radiationhaving various bandwidths for a given spectrum (e.g., narrow bandwidth,broad bandwidth).

For example, one implementation of an LED configured to generateessentially white light (e.g., a white LED) may include a number of dieswhich respectively emit different spectra of electroluminescence that,in combination, mix to form essentially white light. In anotherimplementation, a white light LED may be associated with a phosphormaterial that converts electroluminescence having a first spectrum to adifferent second spectrum. In one example of this implementation,electroluminescence having a relatively short wavelength and narrowbandwidth spectrum “pumps” the phosphor material, which in turn radiateslonger wavelength radiation having a somewhat broader spectrum.

It should also be understood that the term LED does not limit thephysical and/or electrical package type of an LED. For example, asdiscussed above, an LED may refer to a single light emitting devicehaving multiple dies that are configured to respectively emit differentspectra of radiation (e.g., that may or may not be individuallycontrollable). Also, an LED may be associated with a phosphor that isconsidered as an integral part of the LED (e.g., some types of whiteLEDs). In general, the term LED may refer to packaged LEDs, non-packagedLEDs, surface mount LEDs, chip-on-board LEDs, T-package mount LEDs,radial package LEDs, power package LEDs, LEDs including some type ofencasement and/or optical element (e.g., a diffusing lens), etc.

The term “light source” should be understood to refer to any one or moreof a variety of radiation sources, including, but not limited to,LED-based sources (employing one or more LEDs as defined above),incandescent sources (e.g., filament lamps, halogen lamps), fluorescentsources, phosphorescent sources, high-intensity discharge sources (e.g.,sodium vapor, mercury vapor, and metal halide lamps), lasers, othertypes of electroluminescent sources, pyro-luminescent sources (e.g.,flames), candle-luminescent sources (e.g., gas mantles, carbon arcradiation sources), photo-luminescent sources (e.g., gaseous dischargesources), cathode luminescent sources using electronic satiation,galvano-luminescent sources, crystallo-luminescent sources,kine-luminescent sources, thermo-luminescent sources, triboluminescentsources, sonoluminescent sources, radioluminescent sources, andluminescent polymers.

A given light source may be configured to generate electromagneticradiation within the visible spectrum, outside the visible spectrum, ora combination of both. Hence, the terms “light” and “radiation” are usedinterchangeably herein. Additionally, a light source may include as anintegral component one or more filters (e.g., color filters), lenses, orother optical components. Also, it should be understood that lightsources may be configured for a variety of applications, including, butnot limited to, indication and/or illumination. An “illumination source”is a light source that is particularly configured to generate radiationhaving a sufficient intensity to effectively illuminate an interior orexterior space.

The term “spectrum” should be understood to refer to any one or morefrequencies (or wavelengths) of radiation produced by one or more lightsources. Accordingly, the term “spectrum” refers to frequencies (orwavelengths) not only in the visible range, but also frequencies (orwavelengths) in the infrared, ultraviolet, and other areas of theoverall electromagnetic spectrum. Also, a given spectrum may have arelatively narrow bandwidth (essentially few frequency or wavelengthcomponents) or a relatively wide bandwidth (several frequency orwavelength components having various relative strengths). It should alsobe appreciated that a given spectrum may be the result of a mixing oftwo or more other spectra (e.g., mixing radiation respectively emittedfrom multiple light sources).

For purposes of this disclosure, the term “color” is usedinterchangeably with the term “spectrum.” However, the term “color”generally is used to refer primarily to a property of radiation that isperceivable by an observer (although this usage is not intended to limitthe scope of this term). Accordingly, the terms “different colors”implicitly refer to multiple spectra having different wavelengthcomponents and/or bandwidths. It also should be appreciated that theterm “color” may be used in connection with both white and non-whitelight.

The term “color temperature” generally is used herein in connection withwhite light, although this usage is not intended to limit the scope ofthis term. Color temperature essentially refers to a particular colorcontent or shade (e.g., reddish, bluish) of white light. The colortemperature of a given radiation sample conventionally is characterizedaccording to the temperature in degrees Kelvin (K) of a black bodyradiator that radiates essentially the same spectrum as the radiationsample in question. The color temperature of white light generally fallswithin a range of from approximately 700 degrees K (generally consideredthe first visible to the human eye) to over 10,000 degrees K.

Lower color temperatures generally indicate white light having a moresignificant red component or a “warmer feel,” while higher colortemperatures generally indicate white light having a more significantblue component or a “cooler feel.” By way of example, fire has a colortemperature of approximately 1,800 degrees K, a conventionalincandescent bulb has a color temperature of approximately 2848 degreesK, early morning daylight has a color temperature of approximately 3,000degrees K, and overcast midday skies have a color temperature ofapproximately 10,000 degrees K. A color image viewed under white lighthaving a color temperature of approximately 3,000 degree K has arelatively reddish tone, whereas the same color image viewed under whitelight having a color temperature of approximately 10,000 degrees K has arelatively bluish tone.

The terms “lighting unit” and “lighting fixture” are usedinterchangeably herein to refer to an apparatus including one or morelight sources of same or different types. A given lighting unit may haveany one of a variety of mounting arrangements for the light source(s),enclosure/housing arrangements and shapes, and/or electrical andmechanical connection configurations. Additionally, a given lightingunit optionally may be associated with (e.g., include, be coupled toand/or packaged together with) various other components (e.g., controlcircuitry) relating to the operation of the light source(s). An“LED-based lighting unit” refers to a lighting unit that includes one ormore LED-based light sources as discussed above, alone or in combinationwith other non LED-based light sources.

The terms “processor” or “controller” are used herein interchangeably todescribe various apparatus relating to the operation of one or morelight sources. A processor or controller can be implemented in numerousways, such as with dedicated hardware, using one or more microprocessorsthat are programmed using software (e.g., microcode) to perform thevarious functions discussed herein, or as a combination of dedicatedhardware to perform some functions and programmed microprocessors andassociated circuitry to perform other functions.

In various implementations, a processor or controller may be associatedwith one or more storage media (generically referred to herein as“memory,” e.g., volatile and non-volatile computer memory such as RAM,PROM, EPROM, and EEPROM, floppy disks, compact disks, optical disks,magnetic tape, etc.). In some implementations, the storage media may beencoded with one or more programs that, when executed on one or moreprocessors and/or controllers, perform at least some of the functionsdiscussed herein. Various storage media may be fixed within a processoror controller or may be transportable, such that the one or moreprograms stored thereon can be loaded into a processor or controller soas to implement various aspects of the present invention discussedherein. The terms “program” or “computer program” are used herein in ageneric sense to refer to any type of computer code (e.g., software ormicrocode) that can be employed to program one or more processors orcontrollers.

The term “addressable” is used herein to refer to a device (e.g., alight source in general, a lighting unit or fixture, a controller orprocessor associated with one or more light sources or lighting units,other non-lighting related devices, etc.) that is configured to receiveinformation (e.g., data) intended for multiple devices, includingitself, and to selectively respond to particular information intendedfor it. The term “addressable” often is used in connection with anetworked environment (or a “network,” discussed further below), inwhich multiple devices are coupled together via some communicationsmedium or media.

In one network implementation, one or more devices coupled to a networkmay serve as a controller for one or more other devices coupled to thenetwork (e.g., in a master/slave relationship). In anotherimplementation, a networked environment may include one or morededicated controllers that are configured to control one or more of thedevices coupled to the network. Generally, multiple devices coupled tothe network each may have access to data that is present on thecommunications medium or media; however, a given device may be“addressable” in that it is configured to selectively exchange data with(i.e., receive data from and/or transmit data to) the network, based,for example, on one or more particular identifiers (e.g., “addresses”)assigned to it.

The term “network” as used herein refers to any interconnection of twoor more devices (including controllers or processors) that facilitatesthe transport of information (e.g. for device control, data storage,data exchange, etc.) between any two or more devices and/or amongmultiple devices coupled to the network. As should be readilyappreciated, various implementations of networks suitable forinterconnecting multiple devices may include any of a variety of networktopologies and employ any of a variety of communication protocols.Additionally, in various networks according to the present invention,any one connection between two devices may represent a dedicatedconnection between the two systems, or alternatively a non-dedicatedconnection. In addition to carrying information intended for the twodevices, such a non-dedicated connection may carry information notnecessarily intended for either of the two devices (e.g., an opennetwork connection). Furthermore, it should be readily appreciated thatvarious networks of devices as discussed herein may employ one or morewireless, wire/cable, and/or fiber optic links to facilitate informationtransport throughout the network.

The term “user interface” as used herein refers to an interface betweena human user or operator and one or more devices that enablescommunication between the user and the device(s). Examples of userinterfaces that may be employed in various implementations of thepresent invention include, but are not limited to, switches,potentiometers, buttons, dials, sliders, a mouse, keyboard, keypad,various types of game controllers (e.g., joysticks), track balls,display screens, various types of graphical user interfaces (GUIs),touch screens, microphones and other types of sensors that may receivesome form of human-generated stimulus and generate a signal in responsethereto.

It should be appreciated the all combinations of the foregoing conceptsand additional concepts discussed in greater detail below arecontemplated as being part of the inventive subject matter disclosedherein. In particular, all combinations of claimed subject matterappearing at the end of this disclosure are contemplated as being partof the inventive subject matter.

The following patents and patent applications are hereby incorporatedherein by reference:

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BRIEF DESCRIPTION OF THE FIGURES

The following figures depict certain illustrative embodiments of theinvention in which like reference numerals refer to like elements. Thesedepicted embodiments are to be understood as illustrative of theinvention and not as limiting in any way.

FIG. 1 illustrates exemplary operation of conventional A.C. dimmingdevices;

FIG. 2 illustrates a conventional implementation for providing power toan LED- based light source from an A.C. line voltage;

FIG. 3 illustrates a lighting unit including an LED-based light sourceaccording to one embodiment of the invention;

FIG. 4 is a circuit diagram illustrating various components of thelighting unit of FIG. 3, according to one embodiment of the invention;

FIG. 5 illustrates a lighting unit including an LED-based light sourceaccording to another embodiment of the invention;

FIG. 6 is a circuit diagram illustrating various components of thelighting unit of FIG. 5, according to one embodiment of the invention;

FIG. 6A illustrates a lighting unit including an LED-based light sourceaccording to another embodiment of the invention;

FIG. 6B is a circuit diagram illustrating various components of thelighting unit of FIG. 6A, according to one embodiment of the invention;

FIG. 6C is a circuit diagram illustrating various components of thelighting unit of FIG. 6A, according to another embodiment of theinvention;

FIG. 6D shows a dimmable MR-type bulb in a room environment;

FIG. 6E shows a dimmable MR-type bulb in a portable lighting device;

FIG. 6F shows a dimmable MR-type bulb in a retail lighting environment;

FIG. 6G shows a dimmable MR-type bulb in a transportation environment;

FIG. 6H shows a dimmable MR-type bulb in an airplane transportationenvironment;

FIG. 6I shows a dimmable MR-type bulb in an automotive environment;

FIG. 6J shows a reading light with a dimmable MR-type bulb;

FIG. 7 is a block diagram of a processor-based lighting unit includingan LED- based light source according to another embodiment of theinvention;

FIG. 8 is a circuit diagram illustrating various components of the powercircuitry for the lighting unit of FIG. 7;

FIG. 9 is a circuit diagram illustrating a conventional current sinkemployed in driving circuitry for an LED-based light source, accordingto one embodiment of the invention;

FIG. 10 is a circuit diagram illustrating an improved current sink,according to one embodiment of the invention; and

FIG. 11 is a circuit diagram illustrating an improved current sink,according to another embodiment of the invention.

DETAILED DESCRIPTION

1. Overview

Light Emitting Diode (LED) based illumination sources are becoming morepopular in applications where general, task, accent, or other lightingis desired. LED efficiencies, high intensities, low cost, and high levelof controllability are driving demand for LED-based light sources asreplacements for conventional non LED-based light sources.

While conventional A.C. dimming devices as discussed above often areemployed to control conventional light sources such as incandescentlights using an A.C. power source, Applicants have recognized andappreciated that generally such dimmers are not acceptable for use withsolid-state light sources such as LED-based light sources. Stateddifferently, Applicants have identified that LED-based light sources,which operate based on substantially D.C. power sources, generally areincompatible with dimmer circuits that provide A.C. output signals. Thissituation impedes convenient substitution of LED-based light sourcesinto pre-existing lighting systems in which conventional light sourcesare operated via A.C. dimmer circuits.

There are some solutions currently for providing power to LED-basedlighting systems via an A.C. line voltage, but these solutions sufferfrom significant drawbacks if applied to A.C. dimmer circuits. FIG. 2illustrates one such generalized scenario, in which a standard A.C. linevoltage 302 (e.g., 120 Vrms, 220 Vrms, etc.) is used to power anLED-based lighting system, such as a traffic light 808 (the trafficlight includes three modules of LED arrays, one red, one yellow and onegreen, with associated circuitry). In the arrangement of FIG. 2, afull-wave rectifier 802, together with capacitors 800 and 806 andresistor 804, filter the applied A.C. line voltage so as to supply asubstantially D.C. source of power for the traffic light 808. Inparticular, the capacitor 800 may be specifically selected, depending onthe impedance of other circuit components, such that energy is passed tothe traffic light based primarily on the expected frequency of the A.C.line voltage (e.g., 60 Hz).

One problem with the arrangement shown in FIG. 2 if the applied A.C.signal is provided by a dimmer circuit rather than as a line voltage isthat the applied signal may include frequency components that aresignificantly different from the frequency of the line voltage for whichthe circuit was designed. For example, consider a dimmer circuit thatprovides a duty cycle-controlled (i.e., angle modulated) A.C. signal 309such as that shown in FIG. 1; by virtue of the abrupt signal excursionsdue to the “chopping-off” of portions of voltage cycles, signals of thistype include significantly higher frequency components than a typicalline voltage. Were such an angle modulated A.C. signal to be applied tothe arrangement of FIG. 2, the capacitor 800 would allow excess energyassociated with these higher frequency components to pass through to thetraffic light, in most cases causing fatal damage to the light sources.

In view of the foregoing, one embodiment of the present invention isdirected generally to methods and apparatus for facilitating the use ofLED-based light sources on A.C. power circuits that provide either astandard line voltage or that are controlled by conventional dimmers(i.e, “A.C. dimmer circuits”). In one aspect, methods and apparatus ofthe present invention facilitate convenient substitution of LED-basedlight sources in lighting environments employing conventional dimmingdevices and conventional light sources. In yet other aspects, methodsand apparatus according to the present invention facilitate the controlof one or more parameters relating to the light generated by LED-basedlight sources (e.g., intensity, color, color temperature, temporalcharacteristics, etc.) via operation of a conventional dimmer and/orother control signals that may be present in connection with an A.C.line voltage.

Lighting units and systems employing various concepts according to theprinciples of the present invention may be used in a residentialsetting, commercial setting, industrial setting or any other settingwhere conventional A.C. dimmers are found or are desirable. Furthermore,the various concepts disclosed herein may be applied in lighting unitsaccording to the present invention to ensure compatibility of thelighting units with a variety of lighting control protocols that providevarious control signals via an A.C. power circuit.

One example of such a control protocol is given by the X10communications language, which allows X10-compatible products tocommunicate with each other via existing electrical wiring in a home(i.e., wiring that supplies a standard A.C. line voltage). In a typicalX10 implementation, an appliance to be controlled (e.g., lights,thermostats, jacuzzi/hot tub, etc.) is plugged into an X10 receiver,which in turn plugs into a conventional wall socket coupled to the A.C.line voltage. The appliance to be controlled can be assigned with aparticular address. An X10 transmitter/controller is plugged intoanother wall socket coupled to the line voltage, and communicatescontrol commands (e.g., on, off, dim, bright, etc.), via the same wiringproviding the line voltage, to one or more X1 0 receivers based at leastin part on the assigned address(es) (further information regarding X1 0implementations may be found at the website “www.smarthome.com”).According to one embodiment, methods and apparatus of the presentinvention facilitate compatibility of various LED-based light sourcesand lighting units with X1 0 and other communication protocols thatcommunicate control information in connection with an A.C. line voltage.

In general, methods and apparatus according to the present inventionallow a substantially complete retrofitting of a lighting environmentwith solid state LED-based light sources; in particular, pursuant to thepresent invention, the use of LED-based light sources as substitutes forincandescent light sources is not limited to only those A.C. powercircuits that are supplied directly from a line voltage (e.g., via aswitch); rather, methods and apparatus of the present invention allowLED-based light sources to be used in most any conventional (e.g.,incandescent) socket, including those coupled to an A.C. dimmer circuitand/or receiving signals other than a standard line voltage.

In various embodiments, an LED-based lighting unit or fixture accordingto the invention may include a controller to appropriately condition anA.C. signal provided by a dimmer circuit so as to provide power to(i.e., “drive”) one or more LEDs of the lighting unit. The controllermay drive the LED(s) using any of a variety of techniques, includinganalog control techniques, pulse width modulation (PWM) techniques orother power regulation techniques. Although not an essential feature ofthe present invention, in some embodiments the circuitry of theLED-based lighting unit may include one or more microprocessors that areprogrammed to carry out various signal conditioning and/or light controlfunctions. In various implementations of both processor and non-processor based embodiments, an LED-based lighting unit according to theinvention may be configured for operation on an A.C. dimmer circuit withor without provisions for allowing one or more parameters of generatedlight to be adjusted via user operation of the dimmer.

More specifically, in one embodiment, an LED-based lighting unit mayinclude a controller wherein at least a portion of the power deliveredto the controller, as derived from an A.C. dimmer circuit, is regulatedat a substantially constant value over a significant range of dimmeroperation so as to provide an essentially stable power source for thecontroller and other circuitry associated with the lighting unit. In oneaspect of this embodiment, the controller also may be configured tomonitor the adjustable power provided by the dimmer circuit so as topermit adjustment of one or more parameters of the light generated bythe lighting unit in response to operation of the dimmer.

In particular, there are several parameters of light generated by anLED-based light source (other than, or in addition to, intensity orbrightness, for example) that may be controlled in response to dimmeroperation according to the present invention. For example, in variousembodiments, an LED-based lighting unit may be configured such that oneor more properties of the generated light such as color (e.g., hue,saturation or brightness), or the correlated color temperature of whitelight, as well as temporal parameters (e.g., rate of color variation orstrobing of one or more colors) are adjustable via dimmer operation.

As discussed above, in one embodiment, an LED-based lighting unit mayinclude one or more processor-based controllers, including one or morememory storage devices, to facilitate the foregoing and other examplesof adjustable light generation via dimmer operation. In particular, inone embodiment, such a lighting unit may be configured to selectivelyexecute, via dimmer operation, one or more lighting programs stored incontroller memory. Such lighting programs may represent various staticor time-varying lighting effects involving multiple colors, colortemperatures, and intensities of generated light, for example. In oneaspect of this embodiment, the processor-based controller of thelighting unit may be configured to monitor the A.C. signal provided bythe dimmer circuit so as to select different programs and/or programparameters based on one or more changes in the monitored dimmer signalhaving a particular characteristic (e.g., a particular instantaneousvalue relating to the dimmer signal, a particular time averaged valuerelating to the dimmer signal, an interruption of power provided by thedimmer for a predetermined duration, a particular rate of change of thedimmer signal, etc). Upon the selection of a new program or parameter,further operation of the dimmer may adjust the selected parameter orprogram.

In another exemplary embodiment, an LED-based lighting unit according tothe present invention may be configured to be coupled to an A.C. dimmercircuit and essentially recreate the lighting characteristics of aconventional incandescent light as a dimmer is operated to increase ordecrease the intensity of the generated light. In one aspect of thisembodiment, this simulation may be accomplished by simultaneouslyvarying the intensity and the color of the light generated by theLED-based source in response to dimmer operation, so as to approximatethe variable lighting characteristics of an incandescent source whoseintensity is varied. In another aspect of this embodiment, such asimulation is facilitated by a processor-based controller particularlyprogrammed to monitor an A.C. signal provided by the dimmer circuit andrespectively control differently colored LEDs of the lighting unit inresponse to dimmer operation so as to simultaneously vary both theoverall color and intensity of the light generated by the lighting unit.

While many of the lighting effects discussed herein are associated withdimmer compatible control, several effects may be generated according tothe present invention using other control systems as well. For example,the color temperature of an LED- based light source may be programmed toreduce as the intensity is reduced and these lighting changes may becontrolled by a system other than a dimmer system (e.g. wirelesscommunication, wired communication and the like) according to variousembodiments of the invention.

Another embodiment of the present invention is directed to a method forselling, marketing, and advertising of LED-based light sources andlighting systems. The method may include advertising an LED lightingsystem compatible with conventional A.C. dimmers or dimming systems. Themethod may also include advertising an LED light that is compatible withboth dimmable and non-dimmable lighting control systems.

Following below are more detailed descriptions of various conceptsrelated to, and embodiments of, methods and apparatus for providingpower to LED-based lighting according to the present invention. Itshould be appreciated that various aspects of the invention, asdiscussed above and outlined further below, may be implemented in any ofnumerous ways, as the invention is not limited to any particular mannerof implementation. Examples of specific implementations are provided forillustrative purposes only.

2. Non-Processor Based Exemplary Embodiments

As discussed above, according to various embodiments, LED-based lightsources capable of operation via A.C. dimmer circuits may be implementedwith or without microprocessor-based circuitry. In this section, someexamples are given of lighting units that include circuitry configuredto appropriately condition A.C. signals provided by a dimmer circuitwithout the aid of a conventional microprocessor. In the sections thatfollow, a number of processor-based examples are discussed.

FIG. 3 illustrates an LED-based lighting unit 200 according to oneembodiment of the present invention. For purposes of illustration, thelighting unit 200 is depicted generally to resemble a conventionalincandescent light bulb having a screw-type base connector 202 to engagemechanically and electrically with a conventional light socket. Itshould be appreciated, however, that the invention is not limited inthis respect, as a number of other configurations including otherhousing shapes and/or connector types are possible according to otherembodiments. Various examples of power connector configurations include,but are not limited to, screw-type connectors, wedge-type connectors,multi-pin type connectors, and the like, to facilitate engagement withconventional incandescent, halogen, fluorescent or high intensitydischarge (HID) type sockets. Such sockets, in turn, may be connecteddirectly to a source of A.C. power (e.g., line voltage), or via a switchand/or dimmer to the source of A.C. power.

The lighting unit 200 of FIG. 3 includes an LED-based light source 104having one or more LEDs. The lighting unit also includes a controller204 that is configured to receive an A.C. signal 500 via the connector202 and provide operating power to the LED-based light source 104.According to one aspect of this embodiment, the controller 204 includesvarious components to ensure proper operation of the lighting unit forA.C. signals 500 that are provided by a dimmer circuit and, morespecifically, by a dimmer circuit that outputs duty cycle-controlled(i.e., angle modulated) A.C. signals as discussed above.

To this end, according to the embodiment of FIG. 3, the controller 204includes a rectifier 404, a low pass (i.e., high frequency) filter 408and a DC converter 402. In one aspect of this embodiment, the output ofthe DC converter 402 provides an essentially stable DC voltage as apower supply for the LED-based light source 104, regardless of useradjustments of the dimmer that provides the A.C. signal 500. Morespecifically, in this embodiment, the various components of thecontroller 204 facilitate operation of the lighting unit 200 on a dimmercircuit without providing for adjustment of the generated light based ondimmer operation; rather, the primary function of the controller 204 inthe embodiment of FIG. 3 is to ensure that no damage is done to theLED-based light source based on deriving power from an A.C. dimmercircuit.

In particular, according to one aspect of this embodiment, anessentially constant DC power is provided to the LED-based light sourceas long as the dimmer circuit outputs an A.C. signal 500 that providessufficient power to operate the controller 204. In one implementation,the dimmer circuit may output an A.C. signal 500 having a duty cycle ofas low as 50% “on” (i.e., conducting) that provides sufficient power tocause light to be generated by the LED-based light source 104. In yetanother implementation, the dimmer circuit may provide an A.C. signal500 having a duty cycle of as low as 25% or less “on” that providessufficient power to the light source 104. In this manner, useradjustment of the dimmer over a significantly wide range does notsubstantially affect the light output of the lighting unit 200. Again,the foregoing examples are provided primarily for purposes ofillustration, as the invention is not necessarily limited in theserespects.

FIG. 4 is an exemplary circuit diagram that illustrates some of thedetails of the various components shown in FIG. 3, according to oneembodiment of the invention. Again, one of the primary functions of thecircuitry depicted in FIG. 4 is to ensure safe operation of theLED-based light source 104 based on an A.C. signal 500 provided to thelighting unit 200 via a conventional A.C. dimmer circuit. As shown inFIG. 4, the rectifier 404 may be realized by a diode bridge (D47, D48,D49 and D50), while the low pass filter is realized from the variouspassive components (capacitors C2 and C3, inductor L2, and resistors R4and R6) shown in the figure. In this embodiment, the DC converter 402 isrealized in part using the integrated circuit model number TNY264/266manufactured by Power Integrations, Inc., 5245 Hellyer Avenue, San Jose,Calif. 95138 (www.powerint.com), and is configured to provide a 16 VDCsupply voltage to power the LED-based light source 104.

It should be appreciated that filter parameters (e.g., of the low passfilter shown in FIG. 4) are significantly important to ensure properoperation of the controller 204. In particular, the cutoff frequenciesof the filter must be substantially less than a switching frequency ofthe DC converter, but substantially greater than the typical severalcycle cutoff frequency employed in ordinary switch-mode power supplies.According to one implementation, the total input capacitance of thecontroller circuit is such that little energy remains in the capacitorsat the conclusion of each half cycle of the AC waveform. The inductancesimilarly should be chosen to provide adequate isolation of the highfrequency components created by the DC converter to meet regulatoryrequirements (under certain conditions this value may be zero). In yetother implementations, it may be advantageous to place all or part ofthe filter components ahead of the bridge rectifier 404.

The light source 104 of FIG. 4 may include one or more LEDs (as shownfor example as the LEDs D52 and D53 in FIG. 4) having any of a varietyof colors, and multiple LEDs may be configured in a variety of serial orparallel arrangements. Additionally, based on the particularconfiguration of the LED source 104, one or more resistors or othercomponents may be used in serial and/or parallel arrangements with theLED source 104 to appropriately couple the source to the DC supplyvoltage.

According to another embodiment of the invention, an LED-based lightsource not only may be safely powered by an A.C. dimmer circuit, butadditionally the intensity of light generated by the light source may beadjusted via user operation of a dimmer that controls the A.C. signalprovided by the dimmer circuit. FIG. 5 shows another example of alighting unit 200A, similar to the lighting unit shown in FIG. 3, thatis suitable for operation via a dimmer circuit. Unlike the lighting unitshown in FIG. 3, however, the lighting unit 200A of FIG. 5 is configuredto have an adjustable light output that may be controlled via a dimmer.To this end, the controller 204A shown in FIG. 5 includes an additionaladjustment circuit 208 that further conditions a signal output from theDC converter 402. The adjustment circuit 208 in turn provides a variabledrive signal to the LED-based light source 104, based on variations inthe A.C. signal 500 (e.g., variations in the average voltage of thesignal) in response to user operation of the dimmer.

FIG. 6 is an exemplary circuit diagram that illustrates some of thedetails of the various components shown in FIG. 5, according to oneembodiment of the invention. Many of the circuit elements shown in FIG.6 are similar or identical to those shown in FIG. 4. The additionaladjustment circuit 208 is implemented in FIG. 6 in part by the resistorsR2 and R6 which form a voltage divider in the feedback loop of theintegrated circuit U1. A control voltage 410 is derived at the junctionof the resistors R2 and R6, which control voltage varies in response tovariations in the A.C. signal 500 due to dimmer operation. The controlvoltage 410 is applied via diode D5 to a voltage-to- current converterimplemented by resistor R1 and transistor Q1, which provide a variabledrive current to the LED-based light source 104 that tracks adjustmentsof the dimmer's user interface. In this manner, the intensity of thelight generated by the light source 104 may be varied via the dimmerover a significant range of dimmer operation. Of course, it should beappreciated that if the dimmer is adjusted such that the A.C. signal 500is no longer capable of providing adequate power to the associatedcircuitry, the light source 104 merely ceases to produce light.

It should be appreciated that in the circuit of FIG. 6, the controlvoltage 410 is essentially a filtered, scaled, maximum limited versionof average DC voltage fed to the DC converter. This circuit relies onthe DC converter to substantially discharge the input capacitors eachhalf cycle. In practice this is easily achieved because input current tothe controller stays fairly constant or increases as the duty cycle ofthe signal 500 is reduced, so long as device output does not decreasefaster than the control voltage.

FIG. 6A illustrates an LED-based lighting unit 200B according to anotherembodiment of the present invention, in which the lighting unit isdepicted generally to resemble a conventional MR16 bulb having a bi-pinbase connector 202A configured to engage mechanically and electricallywith a conventional MR16 socket. According to one aspect of thisembodiment, the MR16 socket is connected to a source of A.C. power suchthat the A.C. signal 500A received by the unit 200B is a phase-anglemodulated signal on the order of approximately 12 Volts A.C. (e.g.,which may be derived, in turn, from a line voltage controlled via aswitch and/or dimmer). According to other aspects, variousimplementations of the controller 204B shown in FIG. 6A may includecomponents similar to those discussed above in connection with earlierfigures, and may be configured to adjust the light output of theLED-based light source 104 based on variations in the duty cycle of theA.C. signal 500A.

FIGS. 6B and 6C are circuit diagrams illustrating various components ofthe lighting unit of FIG. 6A for different implementations of thecontroller 204B according to various embodiments of the invention. Inboth FIGS. 6B and 6C, the diodes D2-D5 serve as rectificationcomponents, and capacitors C2 and C3 serve as filtering components.

In the embodiment of FIG. 6B, the DC converter comprises the integratedcircuit U6, the transistor switch Q1, the current sense resistor R1, theinductor L1 and the diode D1, and is arranged with the LED-based lightsource 104 (including LEDs D6, D8, D9 and D10) in a “buck” or step-downconfiguration. In the embodiment of FIG. 6C, the integrated circuit U6,the transistor switch Q1, the current sense resistor R1, the inductor L1and the diode D1 are arranged with the LED-based light source 104(including LEDs D9, DI0, D6, D8 and D12) in a “boost” of step-upconfiguration.

In one aspect of these embodiments, the integrated circuit U6 is acurrent-mode pulse-width modulation controller, one example of which isgiven by the MAX5053B available from Maxim Integrated Products,Sunnyvale, Calif. (Maxim product description 19-2590, Rev. 1, November2003, is hereby incorporated herein by reference). The integratedcircuit U6, as well as the other components of the DC converter, areconfigured to provide the LED-based light source 104 with an appropriate5 voltage and power that varies in correspondence to variations in powerprovided by the A.C. signal 500A.

While the specific selection of components and component values shown inFIGS. 6B and 6C is tailored toward operation of the circuits given anA.C. signal 500A on the order of approximately 12 Volts based on theMR16 fixture configuration shown in FIG. 6A, it should be appreciatedthat the invention is not limited in this respect; namely, differentcomponent values may be utilized, employing similar circuitconfigurations to those illustrated in FIGS. 6B and 6C, to realizedimmable control of the LED-based source 104 based on an A.C. signalhaving higher voltages, for use in lighting units having a variety ofphysical configurations (e.g., as discussed above in connection withFIGS. 3 and 5).

Referring to FIG. 6D, in embodiments of the invention, a dimmableMR-type LED bulb or lamp may be disposed in various environments, suchas a room environment 7000. In embodiments such a lamp may disposed as arecessed ceiling mount light 7002, a track light, a desk lamp, a readinglamp, a floor lamp, or the like.

Referring to FIG. 6E, a dimmable MR-type bulb may be disposed in aportable light 8000, such as a handheld light, flashlight, portablelight, helmet light, surgical light, camping light, or the like.

Referring to FIG. 6F, a dimmable MR-type bulb or lamp may be disposed ina retail environment 9000, such as to light retail displays, counters,tabletops, checkout counters, merchandise, or other retail materials.

Referring to FIG. 6G and FIG. 6H, a dimmable MR-type bulb or lamp may bedisposed in a transportation environment, such as a bus 10000, airplane11000, or similar environment. The bulb or lamp may be used as adimmable seat light, a cabin light, a light for a driver or pilot, anaisle light, a bathroom light, a kitchen light, or similar light in suchan environment.

FIG. 6I shows a dimmable MR-type bulb or lamp in an automotiveenvironment. The bulb or lamp may be a cabin light, dashboard light,glove compartment light, seat light, reading light, or similar light forsuch an environment.

FIG. 6J shows a reading light with a dimmable MR-type bulb or lamp. Thereading light may be attachable to a book or other reading material, orit may be a standalone lamp or fixture. The reading light may be a seatlight for a seating environment, such as in a plane, bus, cafe, library,home, or other environment.

In various other embodiments of the invention, a dimmable MR-type bulbor lamp as described herein may comprise or may be disposed in a desklamp, a reading light, a lamp for a retail display, an undercounterlight, a flashlight, a ceiling light, a floor light, a wall light, anaccent light, an ambient light, a recessed down light, an uplight, aretractable arm lamp, a marker light, an automobile interior light, atruck interior light, a motorcycle light, an aircraft interior cabinlight, a helicopter cabin light, a blimp cabin light, a boat cabinlight, a boat bridge light, a submarine light, a train cabin interiorlight, a bus interior reading light, a rocket interior reading light, ashuttle interior reading light, a seat light for a transportationvehicle, passenger area lighting for a transportation vehicle, outdoorlighting for a transportation vehicle, a recreational vehicle light, asnowmobile light, a jet ski light, an ATV light, a dashboard light, abacklight for a gauge, a display light, a headlight for a vehicle, atail light for a vehicle, a signal light for a vehicle, a ground effectslight for a vehicle, an aisle light, a work light for a toolbench, aworkshop light, a hardhat lamp, a diver's lamp, a bicycle lamp, acamping lamp, a portable lamp, a table lamp, a standing floor lamp, abacklight, a TV light, a stereo light, a bookcase light, a spotlight, anindoor spotlight, a display case light, an outdoor spot light, astairway light, an aquarium light, a light on an electrical device, acloset light, a food warming lamp, a music stand lamp, a mixer boardlamp, a hot tub lamp, a signal lamp, a shower light, a bathroom light,an outdoor light, a ceiling fan light, a chandelier light, a tanningbed, a safety light, an emergency light, a stage light, a specialeffects light, a strobe light, an exterior light, an interior light, apost mounted light, a street light, a medical light, an optical light, adental light, a light for disinfecting, a microscope lamp, an x-ray boxbulb, an operating room light, a surgical light, a hospital light, alibrary light, a school light, a photography light, a flash bulb, aholiday light, a Christmas light, a Ramadan light, a menorah light bulb,a simulated candle lamp, a simulated fire, a pool light, a marinelighting and warning system, a highway light, a park light, a pathwaylight, a walkway light, a parking lot light, a dock light, a sign light,a billboard light, a transit shelter light, a siren, a lightbar, anunderwater light, a neon-style sign or a garden light.

3. Processor-Based Exemplary Embodiments

According to other embodiments of the invention, an LED-based lightingunit suitable for operation via an A.C. dimmer circuit may beimplemented using a processor-based controller. Below, an embodiment ofan LED-based lighting unit including a processor is presented, includinga discussion of how such a lighting unit may be particularly configuredfor operation via an A.C. dimmer circuit. For example, in addition to amicroprocessor, such a processor-based lighting unit also may include,and/or receive signal(s) from, one or more other components associatedwith the microprocessor to facilitate the control of the generated lightbased at least in part on user adjustment of a conventional A.C. dimmer.Once a processor-based control scheme is implemented in a lighting unitaccording to the present invention, a virtually limitless number ofconfigurations are possible for controlling the generated light.

FIG. 7 shows a portion of an LED-based lighting unit 200B that includesa processor-based controller 204B according to one embodiment of theinvention. Various examples of processor controlled LED-based lightingunits similar to that described below in connection with FIG. 7 may befound, for example, in U.S. Pat. No. 6,016,038, issued Jan. 18, 2000 toMueller et al., entitled “Multicolored LED Lighting Method andApparatus,” and U.S. Pat. No. 6,211,626, issued Apr. 3, 2001 to Lys etal, entitled “Illumination Components,” which patents are both herebyincorporated herein by reference.

In one aspect, while not shown explicitly in FIG. 7, the lighting unit200B may include a housing structure that is configured similarly to theother lighting units shown in FIGS. 3 and 5 (i.e., as a replacement foran incandescent bulb having a conventional screw-type connector) as wellas FIG. 6B (i.e., as a replacement for an MR16 bulb). Again, however, itshould be appreciated that the invention is not limited to theseexamples; more generally, the lighting unit 200B may be implementedusing any one of a variety of mounting arrangements for the lightsource(s), enclosure/housing arrangements and shapes to partially orfully enclose the light sources, and/or electrical and mechanicalconnection configurations.

As shown in FIG. 7, the lighting unit 200B includes one or more lightsources 104A, 104B, and 104C (shown collectively as 104), wherein one ormore of the light sources may be an LED-based light source that includesone or more light emitting diodes (LEDs). In one aspect of thisembodiment, any two or more of the light sources 104A, 104B, and 104Cmay be adapted to generate radiation of different colors (e.g. red,green, and blue, respectively). Although FIG. 7 shows three lightsources 104A, 104B, and 104C, it should be appreciated that the lightingunit is not limited in this respect, as different numbers and varioustypes of light sources (all LED-based light sources, LED- based andnon-LED-based light sources in combination, etc.) adapted to generateradiation of a variety of different colors, including essentially whitelight, may be employed in the lighting unit 200B, as discussed furtherbelow.

As shown in FIG. 7, the lighting unit 200B also may include a processor102 that is configured to control drive circuitry 109 to drive the lightsources 104A, 104B, and 104C so as to generate various intensities oflight from the light sources. For example, in one implementation, theprocessor 102 may be configured to output via the drive circuitry 109 atleast one control signal for each light source so as to independentlycontrol the intensity of light generated by each light source. Someexamples of control signals that may be generated by the processor anddrive circuitry to control the light sources include, but are notlimited to, pulse modulated signals, pulse width modulated signals(PWM), pulse amplitude modulated signals (PAM), pulse code modulatedsignals (PCM) analog control signals (e.g., current control signals,voltage control signals), combinations and/or modulations of theforegoing signals, or other control signals.

In one implementation of the lighting unit 200B, one or more of thelight sources 104A, 104B, and 104C shown in FIG. 7 may include a groupof multiple LEDs or other types of light sources (e.g., various paralleland/or serial connections of LEDs or other types of light sources) thatare controlled together by the processor 102. Additionally, it should beappreciated that one or more of the light sources 104A, 104B, and 104Cmay include one or more LEDs that are adapted to generate radiationhaving any of a variety of spectra (i.e., wavelengths or wavelengthbands), including, but not limited to, various visible colors (includingessentially white light), various color temperatures of white light,ultraviolet, or infrared. LEDs having a variety of spectral bandwidths(e.g., narrow band, broader band) may be employed in variousimplementations of the lighting unit 200B.

In another aspect of the lighting unit 200B shown in FIG. 7, thelighting unit may be constructed and arranged to produce a wide range ofvariable color radiation. For example, the lighting unit 200B may beparticularly arranged such that the processor- controlled variableintensity light generated by two or more of the light sources combinesto produce a mixed colored light (including essentially white lighthaving a variety of color temperatures). In particular, the color (orcolor temperature) of the mixed colored light may be varied by varyingone or more of the respective intensities of the light sources (e.g., inresponse to one or more control signals output by the processor anddrive circuitry). Furthermore, the processor 102 may be particularlyconfigured (e.g., programmed) to provide control signals to one or moreof the light sources so as to generate a variety of static ortime-varying (dynamic) multi-color (or multi-color temperature) lightingeffects.

Thus, the lighting unit 200B may include a wide variety of colors ofLEDs in various combinations, including two or more of red, green, andblue LEDs to produce a color mix, as well as one or more other LEDs tocreate varying colors and color temperatures of white light. Forexample, red, green and blue can be mixed with amber, white, UV, orange,IR or other colors of LEDs. Such combinations of differently coloredLEDs in the lighting unit 200B can facilitate accurate reproduction of ahost of desirable spectrums of lighting conditions, examples of whichincludes, but are not limited to, a variety of outside daylightequivalents at different times of the day, various interior lightingconditions, lighting conditions to simulate a complex multicoloredbackground, and the like. Other desirable lighting conditions can becreated by removing particular pieces of spectrum that may bespecifically absorbed, attenuated or reflected in certain environments.

As shown in FIG. 7, the lighting unit 200B also may include a memory 114to store various information. For example, the memory 114 may beemployed to store one or more lighting programs for execution by theprocessor 102 (e.g., to generate one or more control signals for thelight sources), as well as various types of data useful for generatingvariable color radiation (e.g., calibration information). The memory 114also may store one or more particular identifiers (e.g., a serialnumber, an address, etc.) that may be used either locally or on a systemlevel to identify the lighting unit 200B. In various embodiments, suchidentifiers may be pre-programmed by a manufacturer, for example, andmay be either alterable or non-alterable thereafter (e.g., via some typeof user interface located on the lighting unit, via one or more data orcontrol signals received by the lighting unit, etc.). Alternatively,such identifiers may be determined at the time of initial use of thelighting unit in the field, and again may be alterable or non- alterablethereafter.

In another aspect, as also shown in FIG. 7, the lighting unit 200Boptionally may be configured to receive a user interface signal 118 thatis provided to facilitate any of a number of user-selectable settings orfunctions (e.g., generally controlling the light output of the lightingunit 200B, changing and/or selecting various pre-programmed lightingeffects to be generated by the lighting unit, changing and/or selectingvarious parameters of selected lighting effects, setting particularidentifiers such as addresses or serial numbers for the lighting unit,etc.). In one embodiment of the invention discussed further below, theuser interface signal 118 may be derived from an A.C. signal provided bya dimmer circuit and/or other control signal(s) on an A.C. powercircuit, so that the light generated by the light source 104 may becontrolled in response to dimmer operation and/or the other controlsignal(s).

More generally, in one aspect of the embodiment shown in FIG. 7, theprocessor 102 of the lighting unit 200B is configured to monitor theuser interface signal 118 and control one or more of the light sources104A, 104B, and 104C based at least in part on the user interfacesignal. For example, the processor 102 may be configured to respond tothe user interface signal by originating one or more control signals(e.g., via the drive circuitry 109) for controlling one or more of thelight sources. Alternatively, the processor 102 may be configured torespond by selecting one or more pre-programmed control signals storedin memory, modifying control signals generated by executing a lightingprogram, selecting and executing a new lighting program from memory, orotherwise affecting the radiation generated by one or more of the lightsources.

To this end, the processor 102 may be configured to use any one or moreof several criteria to “evaluate” the user interface signal 118 andperform one or more functions in response to the user interface signal.For example, the processor 102 may be configured to take some actionbased on a particular instantaneous value of the user interface signal,a change of some characteristic of the user interface signal, a rate ofchange of some characteristic of the user interface signal, a timeaveraged value of some characteristic of the user interface signal,periodic patterns or interruptions of the user interface signal havingparticular durations, zero-crossings of an A.C. user interface signal,etc.

In one embodiment, the processor is configured to digitally sample theuser interface signal 118 and process the samples according to somepredetermined criteria to determine if one or more functions need to beperformed. In yet another embodiment, the memory 114 associated with theprocessor 102 may include one or more tables or, more generally, adatabase, that provides a mapping of values relating to the userinterface signal to values for various control signals used to controlthe LED-based light source 104 (e.g., a particular value or conditionassociated with the user interface signal may correspond to particularduty cycles of PWM signals respectively applied to differently coloredLEDs of the light source). In this manner, a wide variety of lightingcontrol functions may be performed based on the user interface signal.

FIG. 7 also illustrates that the lighting unit 200B may be configured toreceive one or more signals 122 from one or more other signal sources124. In one implementation, the processor 102 of the lighting unit mayuse the signal(s) 122, either alone or in combination with other controlsignals (e.g., signals generated by executing a lighting program, userinterface signals, etc.), so as to control one or more of the lightsources 104A, 104B and 104C in a manner similar to that discussed abovein connection with the user interface. Some examples of a signal source124 that may be employed in, or used in connection with, the lightingunit 200B of FIG. 7 include any of a variety of sensors or transducersthat generate one or more signals 122 in response to some stimulus.Examples of such sensors include, but are not limited to, various typesof environmental condition sensors, such as thermally sensitive (e.g.,temperature, infrared) sensors, humidity sensors, motion sensors,photosensors/light sensors (e.g., sensors that are sensitive to one ormore particular spectra of electromagnetic radiation), various types ofcameras, sound or vibration sensors or other pressure/force transducers(e.g., microphones, piezoelectric devices), and the like.

As also shown in FIG. 7, the lighting unit 200B may include one or morecommunication ports 120 to facilitate coupling of the lighting unit toany of a variety of other devices. For example, one or morecommunication ports 120 may facilitate coupling multiple lighting unitstogether as a networked lighting system, in which at least some of thelighting units are addressable (e.g., have particular identifiers oraddresses) and are responsive to particular data transported across thenetwork.

In particular, in a networked lighting system environment, as data iscommunicated via the network, the processor 102 of each lighting unitcoupled to the network may be configured to be responsive to particulardata (e.g., lighting control commands) that pertain to it (e.g., in somecases, as dictated by the respective identifiers of the networkedlighting units). Once a given processor identifies particular dataintended for it, it may read the data and, for example, change thelighting conditions produced by its light sources according to thereceived data (e.g., by generating appropriate control signals to thelight sources). In one aspect, the memory 114 of each lighting unitcoupled to the network may be loaded, for example, with a table oflighting control signals that correspond with data the processor 102receives. Once the processor 102 receives data from the network, theprocessor may consult the table to select the control signals thatcorrespond to the received data, and control the light sources of thelighting unit accordingly.

In one aspect of this embodiment, the processor 102 of a given lightingunit, whether or not coupled to a network, may be configured tointerpret lighting instructions/data that are received in a DMX protocol(as discussed, for example, in U.S. Pat. Nos. 6,016,038 and 6,211,626),which is a lighting command protocol conventionally employed in thelighting industry for some programmable lighting applications. However,it should be appreciated that lighting units suitable for purposes ofthe present invention are not limited in this respect, as lighting unitsaccording to various embodiments may be configured to be responsive toother types of communication protocols so as to control their respectivelight sources.

The lighting unit 200B of FIG. 7 also includes power circuitry 108 thatis configured to derive power for the lighting unit based on an A.C.signal 500 (e.g., a line voltage, a signal provided by a dimmer circuit,etc.). In one implementation of the lighting unit 200B, the powercircuitry 108 may be configured similarly to portions of the circuitsshown in FIGS. 4 and 6, for example. In particular, FIG. 8 illustratesone exemplary circuit arrangement for the power circuitry 108, based onseveral of the elements shown in FIGS. 4 and 6, that may be employed inone implementation of the lighting unit 200B. In the circuit shown inFIG. 8, a 5 Volt DC output 900 is provided for at least the processor102, whereas a 16 Volt DC output 902 is provided for the drive circuitry109, which ultimately provides power to the LED-based light source 104.Like the circuits shown in FIGS. 4 and 6, it should be appreciated thatas the overall power provided by the A.C. signal 500 is reduced due tooperation of a dimmer, for example, at some point the power circuitry108 will be unable to provide sufficient power to the various componentsof the lighting unit 200B and it will cease to generate light.Nonetheless, in one aspect, the power circuitry 108 is configured toprovide sufficient power to the lighting unit over a significant rangeof dimmer operation.

According to another embodiment of the invention, the power circuitry108 shown in FIG. 8 may be modified to also provide a control signalthat reflects variations in the A.C. signal 500 (e.g., changes in theaverage voltage) in response to dimmer operation. For example, thecircuit of FIG. 8 may be modified to include additional componentssimilar to those shown in connection with the adjustment circuit 208 ofFIG. 6 which provide the control voltage 410 (e.g., a resistor dividernetwork in the opto- isolator feedback loop). A control signal similarlyderived from the circuit of FIG. 8 may serve as the user interfacesignal 118 applied to the processor 102, as indicated by the dashed line410B shown in FIG. 7. In other embodiments, the circuit of FIG. 8 may bemodified so as to derive a control/user interface signal from otherportions of the circuitry, such as an output of the rectifier or lowpass filter, for example.

In yet another embodiment, the user interface signal 118 provided to theprocessor 102 may be the A.C. signal 500 itself, as indicated in FIG. 7by the connections 500B. In this embodiment, the processor 102 may beparticularly programmed to digitally sample the A.C. signal 500 anddetect changes in one or more characteristics of the A.C. signal (e.g.,amplitude variations, degree of angle modulation, etc.). In this manner,rather than respond to a control signal that is derived based onvariations of an average voltage of the A.C. signal 500 due to dimmeroperation, the processor may respond to dimmer operation by “moredirectly” monitoring some characteristic (e.g., the degree of anglemodulation) of the A.C. dimmer output signal. A number of techniquesreadily apparent to those skilled in the art, some of which werediscussed above in connection with the user interface signal 118, may besimilarly implemented by the processor to sample and process the A.C.signal 500.

Once a user interface signal 118 that represents dimmer operation isderived using any of the techniques discussed above (or othertechniques), the processor 102 may Is be programmed to implement any ofa virtually limitless variety of light control functions based on useradjustment of the dimmer. For example, user adjustment of a dimmer maycause the processor to change one or more of the intensity, color,correlated color temperature, or temporal qualities of the lightgenerated by the lighting unit 200B.

To more specifically illustrate the foregoing, consider the lightingunit 200B configured with two lighting programs stored in the memory114; the first lighting program is configured to allow adjustment of theoverall color of the generated light in response to dimmer operation,and the second lighting program is configured to allow adjustment of theoverall intensity of the generated light, at a given color, in responseto dimmer operation. Moreover, the processor is programmed such that aparticular type of dimmer operation toggles between the two programs,and such that on initial power-up, one of the two programs (e.g., thefirst program) is automatically executed as a default.

In this example, on power up, the first program (e.g., adjustable color)begins executing, and a user may change the overall color of thegenerated light by operating the dimmer user interface in a “normal”fashion over some range of adjustment (e.g., the color may be variedthrough a rainbow of colors from red to blue with gradual adjustment ofthe dimmer's user interface).

Once arriving at a desirable color, the user may then select the secondprogram (e.g., adjustable intensity) for execution by operating thedimmer user interface in some particular predetermined manner (e.g.,instantaneously interrupting the power for a predetermined period via anon/off switch incorporated with the dimmer, adjusting the dimmer's userinterface at a quick rate, etc.). As discussed above in connection withuser interface signal concepts, any number of criteria may be used toevaluate dimmer operation and determine if a new program selection isdesired, or if adjustment of a currently executing program is desired.Various examples of program or mode selection via a user interface, aswell as parameter adjustment within a selected program or mode, arediscussed in U.S. Non-provisional application Ser. No. 09/805,368 andU.S. Non- provisional application Ser. No. 10/045,629, incorporatedherein by reference.

In this example, once the second program begins to execute, the user maychange the intensity of the generated light (at the previously adjustedcolor) by subsequent “normal” operation (e.g., gradual adjustment) ofthe dimmer's user interface. Using the foregoing exemplary procedure,the user may adjust both the intensity and the color of the lightemitted from the lighting unit via a conventional A.C. dimmer.

It should be appreciated that the foregoing example is providedprimarily for purposes of illustration, and that the invention is notlimited in these respects. In general, according to various embodimentsof the invention, multiple parameters relating to the generated lightmay be changed in sequence, or simultaneously in combination. Also, viaselection and execution of a lighting program, temporal characteristicsof the generated light also may be adjusted (e.g., rate of strobing of agiven color, rate of change of a rainbow wash of colors, etc.).

For example, in one embodiment, an LED-based light source coupled to anA.C. dimmer circuit may be configured to essentially recreate thelighting characteristics of a conventional incandescent light as adimmer is operated to increase or decrease the intensity of thegenerated light. In one aspect of this embodiment, this simulation maybe accomplished by simultaneously varying the intensity and the color ofthe light generated by the LED-based source via dimmer operation.

More specifically, in conventional incandescent light sources, the colortemperature of the light emitted generally reduces as the powerdissipated by the light source is reduced (e.g., at lower intensitylevels, the correlated color temperature of the light produced may benear 2000K, while the correlated color temperature of the light athigher intensities may be near 3200K). This is why an incandescent lighttends to appear redder as the power to the light source is reduced.Accordingly, in one embodiment, an LED-based lighting unit may beconfigured such that a single dimmer adjustment may be used tosimultaneously change both the intensity and color of the light sourceso as to produce a relatively high correlated color temperature athigher intensities (e.g. when the dimmer provides essentially “full”power) and produce lower correlated color temperatures at lowerintensities, so as to mimic an incandescent source.

Another embodiment of the present invention is directed to a flamesimulation control system, or other simulation control system. Thesystem may include an LED- based light source or lighting unit arrangedto produce flame effects or simulations. Such a flame simulation systemmay be used to replace more conventional flame simulation systems (e.g.incandescent or neon). The flame simulation lighting device may beconfigured (e.g., include a lighting program) for altering theappearance of the generated light to simulate wind blowing through theflame or random flickering effects to make the simulation morerealistic. Such a simulation system may be associated with a userinterface to control the effects, and also may be configured to beadapted for use and/or controlled via an A.C. dimmer circuit (e.g., adimmer control system may be used to change the effects of thesimulation system). In other implementations, the user interface maycommunicate to the simulation device through wired or wirelesscommunication and a user may be able to alter the effects of the devicethrough the user interface. The simulation device may include an effectthat can be modified for rate of change, intensity, color, flicker rate,to simulate windy conditions, still conditions, moderate conditions orany other desirable modification.

Many lighting control systems do not include dimmer circuits wheredimming and other alterable lighting effects would be desirable.Accordingly, yet another embodiment of the present invention is directedto a lighting effect control system including a wireless control system.According to this embodiment, an LED-based light source or lighting unitmay be adapted to receive wireless communications to effect lightingchanges in the lighting system (e.g., see FIG. 7 in connection withcommunication link 120). A wireless transmitter may be used by a user tochange the lighting effects generated by the lighting system. In oneimplementation, the transmitter is associated with a power switch forthe control system. For example, the power switch may be a wall mountedpower switch and a user interface may be associated with thewall-mounted switch. The user interface may be used to generate wirelesscommunication signals that are communicated to the lighting system tocause a change in the light emitted. In another embodiment, the signalsare communicated to the lighting system over the power wires in amultiplexed fashion where the light decodes the data from the power.

Yet another embodiment of the invention is directed to methods andapparatus for communicating control information to one or more lightingdevices, as well as other devices that typically are powered via astandard A.C. line voltage, by using a portion of the duty cycle of theline voltage to communicate the control information. For example,according to one embodiment, a supply voltage controller is configuredto receive a standard A.C. line voltage as an input, and provide as anoutput a power signal including control information. The power signalprovides an essentially constant A.C. power source; however, accordingto one aspect of this embodiment, the signal periodically is“interrupted” (e.g., a portion of the AC duty cycle over a period ofcycles is removed) to provide one or more communication channels overwhich control information (e.g., digitally encoded information) may betransmitted to one or more devices coupled to the power signal. Thedevice(s) coupled to the power signal may be particularly configured tobe responsive in some way to such control information.

For example, it should be appreciated that the various LED-basedlighting units disclosed herein, having the capability to provide powerto LED-based light sources from a standard A.C. line voltage, an A.C.dimmer circuit (e.g., providing an angle modulated power source), orfrom a power source in which other control signals may be present inconnection with an A.C. line voltage, may be particularly configured tobe compatible with the power signal described above and responsive tothe control information transmitted over the communication channel.

According to one aspect of this embodiment, a supply voltage controllerto provide a power signal as discussed above may be implemented as aprocessor-based user interface, including any number of features (e.g.,buttons, dials, sliders, etc.) to facilitate user operation of thecontroller. In particular, in one implementation, the supply voltagecontroller may be implemented to resemble a conventional dimmer (e.g.,having a knob or a slider as a user interface), in which an associatedprocessor is particularly programmed to monitor operation of the userinterface and generate control information in response to suchoperation. The processor also is programmed to transmit the controlinformation via one or more communication channels of the power signal,as discussed above.

In other aspects of this embodiment, unlike currently available homecontrol networks/systems such as X10, the device(s) being controlled bythe power signal essentially are defined by the electrical wiring thatprovides the power signal, rather than by programming or addressesassigned to the device(s). Additionally, other “non- controllable”devices (i.e., not configured to be responsive to the controlinformation transported on the power signal) may be coupled to the powersignal without any detrimental effect, and allow for a mix ofcontrollable and non-controllable devices on the same power circuit(i.e., delivering the same power signal to all devices on the circuit).Moreover, devices in different wiring domains (i.e., on different powercircuits) are guaranteed through topology not to interfere with, or beresponsive to, the power signal on a particular power circuit. In yetanother aspect, the power signal of this embodiment is essentially“transparent” to (i.e., does not interfere with) other protocols such asX10.

In one exemplary implementation based on a supply voltage controllerproviding a power signal as discussed above on a given power circuit, anumber of lighting devices (e.g., conventional lighting devices,LED-based lighting units, etc) may be coupled to the power circuit andconfigured such that they are essentially non-responsive to any controlinformation transmitted on the power circuit. For example, the“non-responsive” lighting devices may be conventional incandescent lightsources or other devices that receive power via the portion of the powersignal that does not include the communication channel. These lightingdevices may serve in a given environment to provide general illuminationin the environment.

In addition to the non-responsive lighting devices in this example, oneor more other controllable lighting devices (e.g., particularlyconfigured LED-based lighting units) also may be coupled to the samepower circuit and configured to be responsive to the control informationin the communication channel of the power signal (i.e., responsive touser operation of the supply voltage controller). In this manner, thecontrollable lighting device(s) may provide various types ofaccent/special effects lighting to complement the general illuminationprovided by the other “non-responsive” devices on the same powercircuit.

4. Exemplary Drive Circuit Embodiments

With reference again to FIG. 7, the drive circuitry 109 of the lightingunit 200B may be implemented in numerous ways, one of which employs oneor more current drivers respectively corresponding to the one or morelight sources 104A, 104B and 104C (collectively 104). In particular,according to one embodiment, the drive circuitry 109 is configured suchthat each differently colored light source is associated with a voltageto current converter that receives a voltage control signal (e.g., adigital PWM signal) from the processor 102 and provides a correspondingcurrent to energize the light source. Such a driver circuit is notlimited to implementations of lighting units that are particularlyconfigured for operation via an A.C. dimmer circuit; more generally,lighting units similar to the lighting unit 200B and configured for usewith various types of power sources (e.g, A.C. line voltages, A.C.dimmer circuits, D.C. power sources) may employ driver circuitryincluding one or more voltage to current converters.

FIG. 9 illustrates one example of a portion of the driver circuitry 109employing a conventional voltage to current converter, also referred toas a “current sink” 910. As shown in FIG. 9, the current sink 910receives a digital input control signal from the processor 102 andprovides a current I_(A) to drive the light source 104A. It should beappreciated that, according to one embodiment, multiple light sourcesare included in the lighting unit, and that the driver circuitry 109includes circuitry similar to that shown in FIG. 9 for each light source(wherein the processor provides one control signal for each currentsink).

The current sink 910 illustrated in FIG. 9 is widely used for control ofcurrent in various applications, and is discussed in many populartextbooks (e.g., see Intuitive IC OPAMPS, Thomas M. Frederiksen, 1984,pages 186-189). The operational amplifier based current sink of FIG. 9functions to maintain the voltage at the node “A” (i.e., across theresistor R6) and the “reference” voltage at the node “C” (at thenon-inverting input of the operational amplifier U1A) at the same value.In this manner, the light source current I_(A) is related to (i.e.,tracks) the digital control signal provided by the processor 102.

The reference voltage at the point “C” in FIG. 9 may be developed in avariety of ways, and the Frederiksen text referenced above suggests thata resistor divider (e.g., R2 and R5) is a good method of creating thisvoltage. Generally, the reference voltage is chosen by a designer of thecircuit as a compromise; on one hand, the voltage should be as low aspossible, to reduce the burden voltage (i.e. the lowest voltage at whichthe current I_(A) is maintained) of the current sink. On the other hand,lowering the reference voltage increases the circuit error, due tovarious sources, including: 1) the offset voltage of the op-amp; 2)differences in the input bias currents of the op-amp; 3) poor tolerancesof low value resistors; and 4) errors in sensing small voltages due tovoltage drops across component interconnections. Lowering the referencevoltage also decreases the speed of the circuit, because feedback to theop-amp is reduced. This situation can also lead to instabilities in thecircuit.

The reference voltage at the point “C” in FIG. 9 need not be constant,and it may be switched between any desired voltages to generatedifferent currents. in particular, a pulse width modulated (PWM) digitalcontrol voltage may be applied to the circuit from the processor 102, togenerate a switched current I_(A). Through careful selection of resistorvalues for the voltage divider formed by resistors R2 and R5, variouscircuit goals may be achieved, including the matching of op-amp biascurrents.

One issue with the circuit shown in FIG. 9 is that when the digitalcontrol signal from the processor is not present or off (e.g., at zerovolts), the operational amplifier U1A may not turn the transistor M1fully off. As a result, some current I_(A) may still flow through thelight source 104A, even though the light source is intended to be off.In view of the foregoing, one embodiment of the present invention isdirected to drive circuitry for LED-based light sources thatincorporates an improved current sink design to ensure more accuratecontrol of the light sources.

FIG. 10 illustrates one example of such an improved current sink 910Aaccording to one embodiment of the invention. The current sink 910A isconfigured such that there 5 is a known “error voltage” at the node “B”(e.g., the inverting input of the operational amplifier U1A), throughthe use of resistors R4 and R1. In particular, the values of resistorsR4 and R1 are selected so as to slightly increase the voltage at thenode “B” as compared to the arrangement shown in FIG. 9. As a result,when the reference voltage at the node “C” is zero (i.e., when thedigital control signal is such that the light source 104A is intended tobe off), the voltage at the node “B” is slightly above that at the node“C”. This voltage difference forces the op-amp to drive its output low,which hence drives transistor M1 well into its “off” region and avoidsany inadvertent flow of the current I_(A).

The small known error voltage introduced at the node “B” does notnecessarily is result in any increase in current error. In oneembodiment, the values of resistors R2 and R5 may be adjusted tocompensate for the effects of the error voltage. For example, resistorsR4 and R1 may be selected to result in 20 mV at the node “B” when thenode “C” is at zero volts (such that the OP AMP is in the “off” state).In the “on” state, the circuit may be configured such that there isapproximately 5 mV of sense voltage at the node “A” (across the resistorR6). The error voltage is added to the desired sense resistor voltage,and the values of resistors R2 and R5 are appropriately selected toresult in a 25 mV reference voltage at the node “C” in the presence of adigital control signal indicating an “on” state. In one embodiment, thecircuit may be configured such that the output current I_(A) and sensevoltage at node “A” may be much greater than the minimums, for variousreasons, but most notably because lower cost op-amps may be used toachieve 1% accuracy if the sense voltage is increased to the 300-700 mVrange.

FIG. 11 shows yet another embodiment of a current sink 910B, in whichseveral optional components are added to the circuit of FIG. 10, whichincrease the speed and current capability of the circuit. In particular,as the size of transistor M1 is increased towards larger currents,capacitor C1 and resistor R3 may be added to compensate for the largercapacitance of M1. This capacitance presents a large load to the op-amp,and for many op-amp designs, this can cause instability. Resistor R3lowers the apparent load presented by M1, and C1 provides a highfrequency feedback path for the op-amp, which bypasses M1. In one aspectof this embodiment, the circuit impedance at nodes “B” and “C” may bematched, to reduce the effects of op-amp bias current. In anotherembodiment this matching may be avoided by using modern FET inputop-amps.

Having thus described several illustrative embodiments of the invention,various alterations, modifications, and improvements will readily occurto those skilled in the art. Such alterations, modifications, andimprovements are intended to be within the spirit and scope of theinvention. While some examples presented herein involve specificcombinations of functions or structural elements, it should beunderstood that those functions and elements may be combined in otherways according to the present invention to accomplish the same ordifferent objectives. In particular, acts, elements and featuresdiscussed in connection with one embodiment are not intended to beexcluded from a similar or other roles in other embodiments.Accordingly, the foregoing description is by way of example only, and isnot intended as limiting.

1. An apparatus, comprising: at least one LED; a housing in which the atleast one LED is disposed, the housing including at least one connectionto engage mechanically and electrically with a conventional MR16 socket;and at least one controller coupled to the housing and the at least oneLED and configured to receive first power from an alternating current(A.C.) dimmer circuit, the A.C. dimmer circuit being controlled by auser interface to vary the first power, the at least one controllerfurther configured to provide second power to the at least one LED basedon the first power.
 2. The apparatus of claim 1, wherein: the A.C.dimmer circuit includes a triac responsive to the user interface so asto variably control a duty cycle of an A.C. signal and thereby vary thefirst power; and the at least one controller is configured to providethe second power as an essentially stable non-varying power to the atleast one LED notwithstanding significant variations of the first power.3. The apparatus of claim 1, wherein: the A.C. dimmer circuit includes atriac responsive to the user interface so as to variably control a dutycycle of an A.C. signal and thereby vary the first power; and the atleast one controller is configured to provide the second power as avarying power to the at least one LED based on variations of the firstpower.
 4. The apparatus of claim 1, wherein: the A.C. dimmer circuitincludes a triac responsive to the user interface so as to variablycontrol a duty cycle of an A.C. signal and thereby vary the first power;and the at least one controller is configured to variably control atleast one parameter of light generated by the at least one LED inresponse to operation of the user interface.
 5. The apparatus of claim4, wherein the at least one parameter of the light that is variablycontrolled by the at least one controller in response to operation ofthe user interface includes at least one of an intensity of the light, acolor of the light, a color temperature of the light, and a temporalcharacteristic of the light.
 6. The apparatus of claim 5, wherein the atleast one LED includes a plurality of differently colored LEDs.
 7. Theapparatus of claim 5, wherein the at least one controller is configuredto variably control at least an intensity and a color of the lightsimultaneously in response to operation of the user interface.
 8. Theapparatus of claim 5, wherein the at least one LED is configured togenerate an essentially white light, and wherein the at least onecontroller is configured to variably control at least an intensity and acolor temperature of the white light simultaneously in response tooperation of the user interface.
 9. The apparatus of claim 8, whereinthe at least one LED includes a plurality of differently colored LEDs.10. An apparatus, comprising: at least one LED; a housing in which theat least one LED is disposed, the housing including at least oneconnection to engage mechanically and electrically with a conventionalMR16 socket; and at least one controller coupled to the housing and theat least one LED and configured to receive a power-related signal froman alternating current (A.C.) power source that provides signals otherthan a standard A.C. line voltage, the at least one controller furtherconfigured to provide power to the at least one LED based on thepower-related signal.
 11. The apparatus of claim 10, wherein the A.C.power source is an (A.C.) dimmer circuit.
 12. The apparatus of claim 11,wherein the A.C. dimmer circuit is controlled by a user interface tovary the power-related signal, and wherein the at least one controlleris configured to provide an essentially non-varying power to the atleast one LED over a significant range of operation of the userinterface.
 13. The apparatus of claim 12, wherein the operation of theuser interface varies a duty cycle of the power-related signal, andwherein the at least one controller is configured to provide theessentially non-varying power to the at least one LED over a significantrange of operation of the user interface notwithstanding variations inthe duty cycle of the power-related signal.
 14. The apparatus of claim12, wherein the at least one controller comprises: a rectifier toreceive the power-related signal and provide a rectified power- relatedsignal; a low pass filter to filter the rectified power-related signal;and a DC converter to provide the essentially non-varying power based onthe filtered rectified power-related signal.
 15. The apparatus of claim14, wherein the housing is structurally configured to resemble an MR16light bulb.
 16. The apparatus of claim 15, wherein the at least one LEDincludes a plurality of differently colored LEDs.
 17. The apparatus ofclaim 1 1, wherein the A.C. dimmer circuit is controlled by a userinterface to vary the power-related signal, and wherein the at least onecontroller is configured to variably control at least one parameter oflight generated by the at least one LED in response to operation of theuser interface.
 18. The apparatus of claim 17, wherein the operation ofthe user interface varies a duty cycle of the power-related signal, andwherein the at least one controller is configured to variably controlthe at least one parameter of the light based at least on the variableduty cycle of the power-related signal.
 19. The apparatus of claim 17,wherein the at least one parameter of the light that is variablycontrolled by the at least one controller in response to operation ofthe user interface includes at least one of an intensity of the light, acolor of the light, a color temperature of the light, and a temporalcharacteristic of the light.
 20. The apparatus of claim 17, wherein theat least one controller is configured to variably control at least twodifferent parameters of the light generated by the at least one LED inresponse to operation of the user interface.
 21. The apparatus of claim20, wherein the at least one controller is configured to variablycontrol at least an intensity and a color of the light simultaneously inresponse to operation of the user interface.
 22. The apparatus of claim20, wherein the at least one LED is configured to generate anessentially white light, and wherein the at least one controller isconfigured to variably control at least an intensity and a colortemperature of the white light simultaneously in response to operationof the user interface.
 23. The apparatus of claim 22, wherein the atleast one controller is configured to variably control at least theintensity and the color temperature of the essentially white light inresponse to operation of the user interface so as to approximate lightgeneration characteristics of an incandescent light source.
 24. Theapparatus of claim 23, wherein the at least one controller is configuredto variably control the color temperature of the essentially white lightover a range from approximately 2000 degrees K at a minimum intensity to3200 degrees K at a maximum intensity.
 25. The apparatus of claim 23,wherein the at least one LED includes a plurality of differently coloredLEDs.
 26. The apparatus of claim 17, wherein the at least one controllerincludes: an adjustment circuit to variably control the at least oneparameter of light based on the varying power-related signal; and powercircuitry to provide at least the power to the at least one LED based onthe varying power-related signal.
 27. The apparatus of claim 26, whereinthe power circuitry includes: a rectifier to receive the power-relatedsignal and provide a rectified power- related signal; a low pass filterto filter the rectified power-related signal; and a DC converter toprovide the power to at least the at least one LED based on the filteredrectified power-related signal.
 28. The apparatus of claim 27, whereinthe adjustment circuit is coupled to the DC converter and is configuredto variably control the at least one LED based on the filtered rectifiedpower-related signal.
 29. The apparatus of claim 27, wherein theadjustment circuit includes at least one processor configured to monitorat least one of the power-related signal, the rectified power-relatedsignal, and the filtered rectified power-related signal so as tovariably control the at least one LED.
 30. The apparatus of claim 29,wherein the power circuitry is configured to provide at least the powerto the at least one LED and power to the at least one processor based onthe varying power-related signal.
 31. The apparatus of claim 29, whereinthe at least one processor is configured to sample the varyingpower-related signal and determine at least one varying characteristicof the varying power-related signal.
 32. The apparatus of claim 29,wherein the operation of the user interface varies a duty cycle of thepower-related signal, and wherein the at least one processor isconfigured to variably control the at least one parameter of the lightbased at least on the varying duty cycle of the power-related signal.33. The apparatus of claim 32, wherein the at least one LED includes aplurality of differently colored LEDs.
 34. The apparatus of claim 33,wherein: the plurality of differently colored LEDs includes: at leastone first LED adapted to output at least first radiation having a firstspectrum; and at least one second LED adapted to output second radiationhaving a second spectrum different than the first spectrum; and the atleast one processor is configured to independently control at least afirst intensity of the first radiation and a second intensity of thesecond radiation in response to operation of the user interface.
 35. Theapparatus of claim 34, wherein the at least one processor is programmedto implement a pulse width modulation (PWM) technique to control atleast the first intensity of the first radiation and the secondintensity of the second radiation.
 36. The apparatus of claim 35,wherein the at least one processor further is programmed to: generate atleast a first PWM signal to control the first intensity of the firstradiation and a second PWM signal to control the second intensity of thesecond ratiadion; and determine duty cycles of the respective first andsecond PWM signals based at least in part on variations in thepower-related signal due to operation of the user interface.
 37. Amethod, comprising an act of: A) providing power via a conventional MR16socket to at least one LED, based on a power-related signal from analternating current (A.C.) power source that provides signals other thana standard A.C. line voltage.
 38. The method of claim 37, wherein theact A) includes an act of: providing power to the at least one LED basedon a power-related signal from an alternating current (A.C.) dimmercircuit.
 39. The method of claim 38, wherein the A.C. dimmer circuit iscontrolled by a user interface to vary the power-related signal, andwherein the act A) comprises an act of: B) providing an essentiallynon-varying power to the at least one LED over a significant range ofoperation of the user interface.
 40. The method of claim 39, wherein theoperation of the user interface varies a duty cycle of the power-relatedsignal, and wherein the act B) includes an act of: providing theessentially non-varying power to the at least one LED over a significantrange of operation of the user interface notwithstanding variations inthe duty cycle of the power-related signal.
 41. The method of claim 39,wherein the act B) includes acts of: rectifying the power-related signalto provide a rectified power-related signal; filtering the rectifiedpower-related signal; and providing the essentially non-varying powerbased on the filtered rectified power- related signal.
 42. The method ofclaim 39, wherein the at least one LED includes a plurality ofdifferently colored LEDs.
 43. The method of claim 38, wherein the A.C.dimmer circuit is controller by a user interface to vary thepower-related signal, and wherein the act A) includes an act of: C)variably controlling at least one parameter of light generated by the atleast one LED in response to operation of the user interface.
 44. Themethod of claim 43, wherein the operation of the user interface varies aduty cycle of the power-related signal, and wherein the act C) includesan act of: D) variably controlling the at least one parameter of thelight based at least on the variable duty cycle of the power-relatedsignal.
 45. The method of claim 43, wherein the act D) includes an actof: variably controlling at least one of an intensity of the light, acolor of the light, a color temperature of the light, and a temporalcharacteristic of the light in response to operation of the userinterface.
 46. The method of claim 43, wherein the act D) includes anact of: E) variably controlling at least two different parameters of thelight generated by the at least one LED in response to operation of theuser interface.
 47. The method of claim 46, wherein the act E) includesan act of: variably controlling at least an intensity and a color of thelight simultaneously in response to operation of the user interface. 48.The method of claim 46, wherein the at least one LED is configured togenerate an essentially white light, and wherein the act E) includes anact of: F) variably controlling at least an intensity and a colortemperature of the white light simultaneously in response to operationof the user interface.
 49. The method of claim 48, wherein the act F)includes an act of: G) variably controlling at least the intensity andthe color temperature of the essentially white light in response tooperation of the user interface so as to approximate light generationcharacteristics of an incandescent light source.
 50. The method of claim49, wherein the act G) includes an act of: variably controlling thecolor temperature of the essentially white light over a range fromapproximately 2000 degrees K at a minimum intensity to 3200 degrees K ata maximum intensity.
 51. The method of claim 50, wherein the at leastone LED includes a plurality of differently colored LEDs.
 52. The methodof claim 43, wherein the act C) includes an act of: H) digitallysampling the varying power-related signal and determine at least onevarying characteristic of the varying power-related signal.
 53. Themethod of claim 52, wherein the operation of the user interface varies aduty cycle of the power-related signal, and wherein the act H) includesan act of: variably controlling the at least one parameter of the lightbased at least on the varying duty cycle of the sampled power-relatedsignal.
 54. The method of claim 43, wherein: the at least one LEDincludes: at least one first LED adapted to output at least firstradiation having a first spectrum; and at least one second LED adaptedto output second radiation having a second spectrum different than thefirst spectrum; and the act C) includes an act of: I) independentlycontrolling at least a first intensity of the first radiation and asecond intensity of the second radiation in response to operation of theuser interface.
 55. The method of claim 54, wherein the act I) includesan act of: J) implementing a pulse width modulation (PWM) technique tocontrol at least the first intensity of the first radiation and thesecond intensity of the second radiation.
 56. The method of claim 55,wherein the act J) includes acts of: generating at least a first PWMsignal to control the first intensity of the first radiation and asecond PWM signal to control the second intensity of the secondratiadion; and determining duty cycles of the respective first andsecond PWM signals based at least in part on variations in thepower-related signal due to operation of the user interface.
 57. Anapparatus, comprising: at least one LED adapted to generate anessentially white light; a housing in which the at least one LED isdisposed, the housing including at least one connection to engagemechanically and electrically with a conventional MR16 socket; and atleast one controller coupled to the at least one LED and configured toreceive a power-related signal from an alternating current (A.C.) dimmercircuit and provide power to the at least one LED based on thepower-related signal, wherein: the A.C. dimmer circuit is controlled bya user interface to vary the power-related signal; and the at least onecontroller is configured to variably control at least one parameter ofthe essentially white light in response to operation of the userinterface so as to approximate light generation characteristics of anincandescent light source.
 58. The apparatus of claim 57, wherein theoperation of the user interface varies a duty cycle of the power-relatedsignal, and wherein the at least one controller is configured tovariably control the at least one parameter of the essentially whitelight based at least on the variable duty cycle of the power-relatedsignal.
 59. The apparatus of claim 58, wherein the housing isstructurally configured to resemble an MR16 light bulb.
 60. Theapparatus of claim 58, wherein the at least one controller is configuredto variably control at least an intensity and a color temperature of theessentially white light simultaneously in response to operation of theuser interface.
 61. The apparatus of claim 60, wherein the at least onecontroller is configured to variably control the color temperature ofthe essentially white light over a range from approximately 2000 degreesK at a minimum intensity to 3200 degrees K at a maximum intensity. 62.The apparatus of claim 61, wherein the at least one LED includes aplurality of differently colored LEDs.
 63. The apparatus of claim 62,wherein: the plurality of differently colored LEDs includes: at leastone first LED adapted to output at least first radiation having a firstspectrum; and at least one second LED adapted to output second radiationhaving a second spectrum different than the first spectrum; and the atleast one controller is configured to independently control at least afirst intensity of the first radiation and a second intensity of thesecond radiation in response to operation of the user interface.
 64. Theapparatus of claim 63, wherein the at least one controller includes atleast one microprocessor programmed to implement a pulse widthmodulation (PWM) technique to control at least the first intensity ofthe first radiation and the second intensity of the second radiation.65. The apparatus of claim 64, wherein the microprocessor further isprogrammed to: generate at least a first PWM signal to control the firstintensity of the first radiation and a second PWM signal to control thesecond intensity of the second radiation; and determine duty cycles ofthe respective first and second PWM signals based at least in part onvariations in the power-related signal due to operation of the userinterface.
 66. The apparatus of claim 65, wherein the microprocessorfurther is programmed to monitor at least one signal representative ofthe variations in the power-related signal.
 67. The apparatus of claim65, wherein the microprocessor further is programmed to directly samplethe power-related signal so as to measure variations in thepower-related signal.